SRPX for treatment of cancer

ABSTRACT

Methods of treating a tumor in a subject include identifying a subject having, at risk for, or suspected of having a tumor, and administering to the subject an effective amount of an SRPX.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase application under 35 U.S.C. §371 ofPCT International Application No. PCT/US2012/055641, filed Sep. 14,2012, which claims the benefit under 35 USC §119(e) of U.S. ProvisionalApplication Ser. No. 61/534,655, filed on Sep. 14, 2011, the entirecontents of these applications are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to treatment of cancers with agents that includea polypeptide.

BACKGROUND

Lung cancer, the leading cause of cancer-related death worldwide, willaccount for an estimated 157,000 deaths in the United States this year.Approximately 85 to 90% of all cases of lung cancer are non-small-celllung cancer (NSCLC). There are three main forms of NSCLC, which areclassified according to histological subtype: adenocarcinoma (accountingfor 40% of lung cancers), squamous cell carcinoma (25%) and large-cellcarcinomas (10%). Advanced-stage NSCLC is currently considered anincurable disease for which standard chemotherapy provides marginalimprovement in overall survival at the expense of substantial morbidityand mortality. Furthermore, fewer than 30% of patients with metastaticNSCLC have a response to platinum-based chemotherapy, the most commonlyused initial treatment in this stage of the disease. Although newerchemotherapeutic agents, such as bevacizumab, have been introduced, themedian overall survival of patients with metastatic NSCLC remainsapproximately 1 year (Sandler et al., 2006, N. Engl. J. Med., 355:2542;Schiller et al., 2002, N. Engl. J. Med., 346:92), and only 3 to 4% ofpatients with metastatic NSCLC survive 5 years after diagnosis.

SUMMARY

This disclosure is based, in part, on the surprising discovery that,although previously believed to be active intracellularly (see, e.g.,Tambe et al., Tambe et al. 2007, Carcinogenesis 28(4):777-784,especially FIG. 4B, which suggests that SRPX is localized to theendoplasmic reticulum), a secreted form of the Sushi-Repeat-containingProtein, X-linked (SRPX) protein induces senescence and/or apoptosis incancer cells. Described herein are methods of diagnosing and treatingtumors (e.g., cancers), inducing cellular apoptosis, inducing cellularsenescence, and inhibiting cellular proliferation using SRPX agents,e.g., agents comprising SRPX polypeptides delivered to the extracellularsurface of tumor cells, or comprising cells (e.g., autologous cells)expressing and secreting exogenous SRPX polypeptides and implanted intoor near the tumor.

In one aspect, this application features methods of treating a tumor ina subject by identifying a subject having, at risk for, or suspected ofhaving a tumor; and administering to the extracellular surface of tumorcells in the subject an effective amount of an SRPX agent, e.g.,polypeptide or active fragment thereof, thereby treating the tumor. Insome embodiments, the tumor is a cancer (e.g., a lung cancer (e.g., anon-small cell lung carcinoma, small-cell carcinoma, adenocarcinoma, orsquamous cell carcinoma), a melanoma, carcinoma, breast cancer, ovariancancer, pancreatic cancer, colorectal carcinoma, or papillary thyroidcarcinoma). In some embodiments, the tumor comprises cells in whichexpression of SRPX is significantly reduced, e.g., undetectable, ascompared to wild-type (normal) cells of the same tissue. In someembodiments, the methods include identifying a subject as having a tumorin which expression of SRPX is significantly reduced, e.g., by detectingexpression of SRPX in a sample comprising cells from the tumor.

In another aspect, this application features methods of inducingsenescence in a cell (e.g., a tumor cell or cancer cell) that includeadministering to the extracellular surface of the cell an effectiveamount of a SRPX agent, e.g., polypeptide or active fragment thereof. Insome embodiments, the cell is a tumor cell.

In a further aspect, this application features methods of inducingapoptosis in a cell (e.g., a tumor cell or cancer cell) that includeadministering to the extracellular surface of the cell an effectiveamount of a SRPX agent, e.g., polypeptide or active fragment thereof.

In another aspect, this application features methods of inhibitingproliferation of a cell (e.g., a tumor cell or cancer cell) that includeadministering to the extracellular surface of the cell an effectiveamount of a SRPX agent, e.g., polypeptide or active fragment thereof.

In a further aspect, this application features methods of inhibitinggrowth (e.g., metastatic growth) in a subject of a tumor that includeadministering to the extracellular surface of cells of the tumor in thesubject an effective amount of a SRPX agent, e.g., polypeptide or activefragment thereof.

In some embodiments, expression of SRPX is significantly reduced, e.g.,undetectable, in the cell as compared to a wild-type (normal) cell ofthe same type/tissue type. In some embodiments, the methods includeidentifying a cell in which expression of SRPX is significantly reduced,e.g., by detecting expression of SRPX in a sample comprising cells froma tumor.

In another aspect, this application features the use of a SRPX agent inthe preparation of a medicament for the treatment of a tumor or cancer(e.g., a lung cancer (e.g., a non-small cell lung carcinoma, small-cellcarcinoma, adenocarcinoma, or squamous cell carcinoma), a melanoma,carcinoma, breast cancer, ovarian cancer, pancreatic cancer, colorectalcarcinoma, or papillary thyroid carcinoma) in a subject. Compositionscomprising a SRPX polypeptide or active fragment thereof are suitablefor administration to the extracellular surface of cells in the tumor.In some embodiments, the tumor or cancer is metastatic.

In a further aspect, this application features an isolated SRPX agentfor treating a tumor or cancer (e.g., a lung cancer (e.g., a non-smallcell lung carcinoma, small-cell carcinoma, adenocarcinoma, or squamouscell carcinoma), a melanoma, carcinoma, breast cancer, ovarian cancer,pancreatic cancer, colorectal carcinoma, or papillary thyroid carcinoma)in a subject. Compositions comprising a SRPX polypeptide or activefragment thereof are suitable for administration to the extracellularsurface of cells in the tumor. In some embodiments, the tumor or canceris metastatic.

In some embodiments, the tumor comprises cells in which expression ofSRPX is significantly reduced, e.g., undetectable, as compared towild-type (normal) cells of the same tissue. In some embodiments, themethods include identifying a subject as having a tumor in whichexpression of SRPX is significantly reduced, e.g., by detectingexpression of SRPX in a sample comprising cells from the tumor.

In some embodiments, the SRPX agent is a composition that includes apolypeptide having a sequence at least 80% identical (e.g., at least85%, 90%, 95%, 98%, or 99% identical) to SEQ ID NO:1 or SEQ ID NO:2, oran active fragment of either. The polypeptide can be conjugated to aheterologous moiety (e.g., a heterologous polypeptide sequence). In someembodiments, the SRPX agent includes a functional fragment or domain ofSEQ ID NO:1 or SEQ ID NO:2, or a fragment of either. The SRPX agent canbe administered, e.g., topically, systemically, or locally (e.g., by adrug-releasing implant). The SRPX polypeptide is administered to theextracellular surface of cells in the tumor.

In some embodiments, the SRPX agent is administered by introducing intothe subject a composition that induces the expression of SRPX or anactive fragment or analog thereof, e.g., a nucleic acid encoding apolypeptide that includes a sequence at least 80% identical (e.g., atleast 85%, 90%, 95%, 98%, or 99% identical) to SEQ ID NO:1 or SEQ IDNO:2, or a fragment of either. The nucleic acid can be in a vector,e.g., a viral vector (e.g., an adenovirus vector, an adeno-associatedvirus vector, a retrovirus vector, or a lentivirus vector). In someembodiments, the SRPX agent is administered by introducing into thesubject a cell that includes a nucleic acid encoding a polypeptide thatincludes a sequence at least 80% identical (e.g., at least 85%, 90%,95%, 98%, or 99% identical) to SEQ ID NO:1 or SEQ ID NO:2, or a fragmentof either, and wherein the cell secretes the polypeptide.

In another aspect, the invention features methods for treating a tumorin a subject. The methods include identifying a subject having, at riskfor, or suspected of having a tumor; and administering to the subject aneffective amount of a population of cells expressing a nucleic acidencoding a polypeptide that is at least 95% identical to SEQ ID NO:1,wherein the cells are administered into or near the tumor, therebytreating the tumor.

An active or functional fragment is a portion of the SRPX protein thatretains the ability to induce cancer cell senescence and/or apoptosis,e.g., is able to induce cancer cell death or senescence (e.g., lungcancer cell death or senescence) in a relevant assay known in the art,e.g., an assay described herein.

“Polypeptide” and “protein” are used interchangeably and mean anypeptide-linked chain of amino acids, regardless of length orpost-translational modification.

As used herein, a subject “at risk of developing cancer” is a subjectthat has a predisposition to develop cancer, i.e., a genetic or familialpredisposition to develop cancer or has been exposed to conditions thatcan result in cancer. From the above it will be clear that subjects “atrisk of developing cancer” are not all subjects.

A subject “suspected of having cancer” is one having one or moresymptoms of cancer. Symptoms of cancer are well-known to those of skillin the art and include, without limitation, weight loss, weakness,excessive fatigue, difficulty eating, loss of appetite, unusual molefeatures, newly pigmented skin area, skin growths, skin ulcers, skinlumps, chronic cough, worsening breathlessness, breathing difficulty,enlarged lymph nodes, coughing up blood, blood in the urine, blood instool, nausea, vomiting, liver metastases, lung metastases, bonemetastases, breast or nipple changes, nipple discharge, abdominalfullness, bloating, fluid in peritoneal cavity, constipation, abdominaldistension, perforation of colon, acute peritonitis (infection, fever,pain), vaginal bleeding, pain, vomiting blood, heavy sweating, fever,high blood pressure, anemia, diarrhea, jaundice, dizziness, chills,muscle spasms, colon metastases, lung metastases, bladder metastases,liver metastases, bone metastases, kidney metastases, pancreasmetastases, difficulty swallowing, and the like. For example, a patientwho has been diagnosed by a physician as having cancer is stillsuspected of having cancer.

The term “cancer” refers to cells having the capacity for autonomousgrowth. Examples of such cells include cells having an abnormal state orcondition characterized by rapidly proliferating cell growth. The termis meant to include cancerous growths, e.g., tumors; oncogenicprocesses, metastatic tissues, and malignantly transformed cells,tissues, or organs, irrespective of histopathologic type or stage ofinvasiveness. Also included are malignancies of the various organsystems, such as respiratory, cardiovascular, renal, reproductive,hematological, neurological, hepatic, gastrointestinal, and endocrinesystems; as well as adenocarcinomas which include malignancies such asmost colon cancers, renal-cell carcinoma, prostate cancer and/ortesticular tumors, non-small cell carcinoma of the lung, cancer of thesmall intestine, and cancer of the esophagus. Cancer that is “naturallyarising” includes any cancer that is not experimentally induced byimplantation of cancer cells into a subject, and includes, for example,spontaneously arising cancer, cancer caused by exposure of a patient toa carcinogen(s), cancer resulting from insertion of a transgeniconcogene or knockout of a tumor suppressor gene, and cancer caused byinfections, e.g., viral infections. The term “carcinoma” is artrecognized and refers to malignancies of epithelial or endocrinetissues. In some embodiments, the present methods can be used to treat asubject having an epithelial cancer, e.g., a solid tumor of epithelialorigin, e.g., lung, breast, ovarian, prostate, renal, pancreatic, orcolon cancer.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods andmaterials are described below. All publications, patent applications,patents, and other references mentioned herein are incorporated byreference in their entirety. In case of conflict, the presentspecification, including definitions, will control. In addition, thematerials, methods, and examples are illustrative only and not intendedto be limiting.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is a bar graph depicting relative SRPX expression in normal lungtissue and tumor samples from patients with lung adenocarcinomas andsquamous cell carcinomas.

FIG. 1B is a photograph showing growth of a normal lung cell line (MRC5)and lung cancer cell lines (NCH-H23, EKVX, HOP-62, and HOP-92) grown inthe presence (+) or absence (—) of rSRPX.

FIGS. 1C and 1D are line graphs depicting tumor growth in mice withtumor xenografts treated with a control vector (AAV-LacZ) or a vectorexpressing SRPX (AAV-SRPX).

FIGS. 1E and 1F are line graphs showing levels of alanineaminotransferase (ALT, 1E) and aspartate aminotransferase (AST, 1F) inanimals administered the indicated doses of SRPX. No significantincreases were seen in either ALT or AST.

FIG. 2 is a bar graph depicting relative growth of breast, colon,leukemia, lung, and melanoma cancer cell lines without treatment ortreated with control conditioned media (CM) or CM containing SRPX.

FIG. 3A is a photograph showing growth of a human lung adenocarcinomacell line (A549) treated in the presence of control CM, SRPX-containingCM or SRPX(Δ1-35)-containing CM.

FIG. 3B is a bar graph depicting the percent apoptosis, as assessed byAnnexin V staining, in A549 cells transfected with a vector expressingSRPX or SRPX(Δ1-35).

FIG. 3C is an immunoblot showing expression of SRPX and SRPX(Δ1-35) incell lysate and CM.

FIG. 4A is a plasmid map of pAAVCMVPI.SRPXsec.

FIG. 4B is a map of adeno-associated vector AAV-SRPXsec.

FIGS. 4C-4D depict the sequence of plasmid pAAVCMVPI.SRPXsec (SEQ IDNO:5), which includes an adeno associated vector (AAV) expressing thepolypeptide of SEQ ID NO:1 with a heterologous signal sequence andC-terminal Myc and His₆ tags.

FIG. 5A is a plasmid map of pAAVCMVPI.SRPXwt.

FIG. 5B is a map of adeno-associated vector AAV-SRPXwt.

FIGS. 5C-5D depict the sequence of plasmid pAAVCMVPI.SRPXwt (SEQ IDNO:6), which includes an AAV expressing the polypeptide of SEQ ID NO:2with C-terminal Myc and His₆ tags.

DETAILED DESCRIPTION

This disclosure includes methods of treating tumors (e.g., cancers),inducing cellular apoptosis, inducing cellular senescence, andinhibiting cellular proliferation with SRPX agents.

SRPX Agents

SRPX agents that can be used with the methods described herein areagents that include an SRPX polypeptide sequence and, alternatively, oneor more polypeptide or non-polypeptide moieties, such that the agent hasat least 25% (e.g., at least: 30%; 40%; 50%; 60%; 70%; 75%; 80%; 85%;90%; 95%; 97%; 98%; 99%; 99.5%, or 100% or even greater) of the abilityof rSRPX (see Example 1) to inhibit the proliferation of one or more ofNCI-H23, EKVX, HOP-62, HOP-92, HCT-15, SW-620, COLO205, HT29, HCT-116,KM-12, CCRF-CEM, K-562, MOLT-4, SR, RPMI-8226, A549-ATCC, NCI-H226,NCI-H322M in vitro. Exemplary agents include fragments and analogs ofSRPX (see below). The SRPX polypeptide sequence can include a mature,soluble SRPX polypeptide (e.g., SEQ ID NO:1 or residues 29, 30, 31, 32,33, 34 or 35 to 464 of SEQ ID NO:2), one or more domains of SRPX, orfragments or variants thereof. Exemplary fragments of SRPX includeresidues 59 to 115, 59 to 175, 59 to 254, 59 to 317, 120 to 175, 120 to254, 120 to 317, 175 to 254, 175 to 317, and 262 to 317 of SEQ ID NO:2.An exemplary mature, soluble SRPX polypeptide is provided as:

(SEQ ID NO: 1) DSPLEDDEVGYSHPRYKDTPWCSPIKVKYGDVYCRAPQGGYYKTALGTRCDIRCQKGYELHGSSLLICQSNKRWSDKVICKQKRCPTLAMPANGGFKCVDGAYFNSRCEYYCSPGYTLKGERTVTCMDNKAWSGRPASCVDMEPPRIKCPSVKERIAEPNKLTVRVSWETPEGRDTADGILTDVILKGLPPGSNFPEGDHKIQYTVYDRAENKGTCKFRVKVRVKRCGKLNAPENGYMKCSSDGDNYGATCEFSCIGGYELQGSPARVCQSNLAWSGTEPTCAAMNVNVGVRTAAALLDQFYEKRRLLIVSTPTARNLLYRLQLGMLQQAQCGLDLRHITVVELVGVFPTLIGRIGAKIMPPALALQLRLLLRIPLYSFSMVLVDKHGMDKERYVSLVMPVALFNLIDTFPLRKEEMVLQAEMSQTCNT

In certain embodiments, SRPX polypeptides include sequencessubstantially identical to all or a portion of a naturally occurringSRPX polypeptide. Polypeptides “substantially identical” to the SRPXpolypeptide sequence described herein can contain an amino acid sequencethat is at least 65% (e.g., at least 75%, 80%, 85%, 90%, 95%, 98%, or99%, e.g., 100%), identical to the amino acid sequences of the SRPXpolypeptide represented by SEQ ID NO:1, an amino acid sequence ofGenBank Accession No. NP_(—)006298.1 (SEQ ID NO:2), NP_(—)001164221.1(residues 1 to 32 and 53 to 464 of SEQ ID NO:2), NP_(—)001164222.1 (SEQID NO:7), or NP_(—)001164223.1 (SEQ ID NO:8), or a fragment as disclosedherein (e.g., residues 29, 30, 31, 32, 33, 34, 35, or 36 to 464 of SEQID NO:2 or residues 59 to 115, 59 to 175, 59 to 254, 59 to 317, 120 to175, 120 to 254, 120 to 317, 175 to 254, 175 to 317, and 262 to 317 ofSEQ ID NO:2). The human NP_(—)006298.1 sequence is shown below.

(SEQ ID NO: 2) MGSPAHRPALLLLLPPLLLLLLLRVPPSRSFPGSGDSPLEDDEVGYSHPRYKDTPWCSPIKVKYGDVYCRAPQGGYYKTALGTRCDIRCQKGYELHGSSLLICQSNKRWSDKVICKQKRCPTLAMPANGGFKCVDGAYFNSRCEYYCSPGYTLKGERTVTCMDNKAWSGRPASCVDMEPPRIKCPSVKERIAEPNKLTVRVSWETPEGRDTADGILTDVILKGLPPGSNFPEGDHKIQYTVYDRAENKGTCKFRVKVRVKRCGKLNAPENGYMKCSSDGDNYGATCEFSCIGGYELQGSPARVCQSNLAWSGTEPTCAAMNVNVGVRTAAALLDQFYEKRRLLIVSTPTARNLLYRLQLGMLQQAQCGLDLRHITVVELVGVFPTLIGRIGAKIMPPALALQLRLLLRIPLYSFSMVLVDKHGMDKERYVSLVMPVALFNLIDTFPLRKEEMVLQAEMSQTCNT

The human NP_(—)001164222.1 sequence is shown below.

(SEQ ID NO: 7) MGSPAHRPALLLLLPPLLLLLLLRVPPSRSFPGSGDSPLEDDEVGYSHPRYKDTPWCSPIKVKYGDVYCRAPQGGYYKTALGTRCDIRCQKGYELHGSSLLICQSNKRWSDKVICKHMEPPRIKCPSVKERIAEPNKLTVRVSWETPEGRDTADGILTDVILKGLPPGSNFPEGDHKIQYTVYDRAENKGTCKFRVKVRVKRCGKLNAPENGYMKCSSDGDNYGATCEFSCIGGYELQGSPARVCQSNLAWSGTEPTCAAMNVNVGVRTAAALLDQFYEKRRLLIVSTPTARNLLYRLQLGMLQQAQCGLDLRHITVVELVGVFPTLIGRIGAKIMPPALALQLRLLLRIPLYSFSMVLVDKHGMDKERYVSLVMPVALFNLIDTFPLRKEE MVLQAEMSQTCNT

The human NP_(—)001164223.1 sequence is shown below.

(SEQ ID NO: 8) MGSPAHRPALLLLLPPLLLLLLLRVPPSRSFPGSGDSPLEDDEVGYSHPRYKDTPWCSPIKVKYGDVYCRAPQGGYYKTALGTRCDIRCQKGYELHGSSLLICQSNKRWSDKVICKQKRCPTLAMPANGGFKCVDGAYFNSRCEYYCSPGYTLKGERTVTCMDNKAWSGRPASCVDMEPPRIKCPSVKERIAEPNKLTVRVSWETPEGRDTADGILTDVILKGLPPGSNFPEGDHKIQYTVYDRAENKGTCKFRVKVRVKRCGKLNAPENGYMKCSSDGDNYGATCEFSCIGGYELQGSPARVCQSNLAWSGTEPTCAAMNVNVGVRTAAALLDQFYEKRRLLIVSTPTARNLLYRLQLGMLQAVAANPTLLLQYGASG

Any of the above polypeptides can be provided in mature form without thesignal sequence (e.g., residues 1 to 29, 30, 31, 32, 33, 34, or 35 ofSEQ ID NO: 2, 7, or 8).

Furthermore, a SRPX polypeptide (e.g., SEQ ID NO:1, an amino acidsequence of GenBank Accession No. NP_(—)006298.1 (SEQ ID NO:2),NP_(—)001164221.1, NP_(—)001164222.1, or NP_(—)006298.1, or a fragmentas disclosed herein (e.g., residues 29, 30, 31, 32, 33, 34 or 35 to 464of SEQ ID NO:2 or residues 59 to 115, 59 to 175, 59 to 254, 59 to 317,120 to 175, 120 to 254, 120 to 317, 175 to 254, 175 to 317, and 262 to317 of SEQ ID NO:2)) with up to 50, e.g., 1, 3, 5, 10, 15, 20, 25, 30,or 40, amino acid insertions, deletions, or substitutions (e.g.,conservative amino acid substitutions) will be useful in thecompositions and methods described herein. A “conservative amino acidsubstitution” is one in which the amino acid residue is replaced with anamino acid residue having a similar side chain. Families of amino acidresidues having similar side chains have been defined in the art. Thesefamilies include amino acids with basic side chains (e.g., lysine,arginine, histidine), acidic side chains (e.g., aspartic acid, glutamicacid), uncharged polar side chains (e.g., glycine, asparagine,glutamine, serine, threonine, tyrosine, cysteine), nonpolar side chains(e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine,methionine, tryptophan), beta-branched side chains (e.g., threonine,valine, isoleucine) and aromatic side chains (e.g., tyrosine,phenylalanine, tryptophan, histidine).

The percent identity between two amino acid sequences can be determinedusing the BLAST 2.0 program, which is available to the public atncbi.nlm.nih.gov/BLAST. Sequence comparison is performed using thedefault parameters (BLOSUM 62 matrix, gap existence cost of 11, perresidue gap cost of 1, and a lambda ratio of 0.85). The mathematicalalgorithm used in BLAST programs is described in Altschul et al., 1997,Nucleic Acids Research, 25:3389-3402.

SRPX polypeptides useful in the methods described herein can be, but arenot limited to, recombinant polypeptides and naturally occurringpolypeptides. A SRPX polypeptide can be obtained from any human ormammalian species, and include alternatively spliced forms and otherisoforms that have the disclosed activities. Non-human SRPX polypeptideswith similarity to human SRPX polypeptides have been identified inchimpanzees (e.g., GenBank Accession No. XP_(—)521003.3), rhesus monkeys(e.g., GenBank Accession Nos. XP_(—)001083979.1, XP_(—)001084091.1),common marmosets (e.g., GenBank Accession Nos. XP_(—)002762821.1,XP_(—)002762820.1), Sumatran orangutans (GenBank Accession Nos.XP_(—)002831567.1, XP_(—)002831566.1), white-cheeked gibbons (GenBankAccession No. XP_(—)003271118.1), cattle (e.g., GenBank Accession Nos.DAA12706.1, NP_(—)001035579.1), horses (e.g., GenBank Accession No.XP_(—)001489693.3), dogs (e.g., GenBank Accession No. XP_(—)548948.3),mice (e.g., GenBank Accession Nos. CAM18748.1, NP_(—)058607.1), and rats(e.g., GenBank Accession Nos. AAH87639.1, NP_(—)071969.1).

Also useful in the new methods are fusion proteins in which a portion ofa SRPX polypeptide is fused to an unrelated polypeptide (e.g., a markerpolypeptide or purification tag) to create a fusion protein. Forexample, the polypeptide can be fused to a peptide tag to facilitatepurification (e.g., a hexa-histidine tag or a FLAG tag to facilitatepurification of bacterially expressed polypeptides or to a hemagglutinintag or a FLAG tag to facilitate purification of polypeptides expressedin eukaryotic cells). Also useful are, for example, polypeptides thatinclude a first portion and a second portion; the first portionincludes, e.g., a SRPX polypeptide, and the second portion includes,e.g., a detectable marker or a serum protein, e.g., an immunoglobulinconstant region, or human serum albumin.

SRPX contains three complement control protein (CCP) modules (aka shortconsensus repeats (SCRs) or SUSHI repeats; Norman et al., J. Mol. Biol.,219:717-725; Kirkitadze et al., 2001, Immunol. Rev., 180:146-161) atresidues 59 to 115, 120 to 175, and 262 to 317 of SEQ ID NO:2.Additionally, the protein contains a hyaline repeat (HYR) domain atresidues 175 to 254 of SEQ ID NO:2. Exemplary fragments of SRPX caninclude one or more of residues 59 to 115, 59 to 175, 59 to 254, 59 to317, 120 to 175, 120 to 254, 120 to 317, 175 to 254, 175 to 317, or 262to 317 of SEQ ID NO:2. Conserved residues and domains can be used whenproducing fragments, analogs, and variants of SRPX polypeptides.

A SRPX agent can have one or more chemical modifications (e.g.,posttranslational modifications) at one or more sites on thepolypeptide, e.g., at the amino or carboxy terminus. Methods of chemicalmodification are well-known to those of skill in the art, and can beused to alter one or more properties, e.g., activity, stability,retention, or pharmacokinetics of the SRPX agent. Exemplarymodifications include glycosylation and PEGylation. SRPX contains aputative O-glycosylation site at residue 383 of SEQ ID NO:2. Pegylationof proteins is described in US 2006/0100144. Similar modifications andmethods can be used with SRPX agents.

A SRPX agent can also be a peptidomimetic version of a SRPX polypeptide(e.g., SEQ ID NO:1), functional fragment, or variant thereof. Thesepolypeptides can be modified according to the methods known in the artfor producing peptidomimetics. See, e.g., Kazmierski, W. M., ed.,Peptidomimetics Protocols, Human Press (Totowa N.J. 1998); Goodman etal., eds., Houben-Weyl Methods of Organic Chemistry: Synthesis ofPeptides and Peptidomimetics, Thiele Verlag (New York 2003); and Mayo etal., J. Biol. Chem., 278:45746 (2003). In some cases, these modifiedpeptidomimetic versions of the peptides and fragments disclosed hereinexhibit enhanced stability in vivo, relative to the non-peptidomimeticpeptides.

Methods for creating a peptidomimetic include substituting one or more,e.g., all, of the amino acids in a peptide sequence with D-amino acidenantiomers. Such sequences are referred to herein as “retro” sequences.In another method, the N-terminal to C-terminal order of the amino acidresidues is reversed, such that the order of amino acid residues fromthe N-terminus to the C-terminus of the original peptide becomes theorder of amino acid residues from the C-terminus to the N-terminus inthe modified peptidomimetic. Such sequences can be referred to as“inverso” sequences.

Peptidomimetics can be both the retro and inverso versions, i.e., the“retro-inverso” version of a peptide disclosed herein. The newpeptidomimetics can be composed of D-amino acids arranged so that theorder of amino acid residues from the N-terminus to the C-terminus inthe peptidomimetic corresponds to the order of amino acid residues fromthe C-terminus to the N-terminus in the original peptide.

Other methods for making a peptidomimetics include replacing one or moreamino acid residues in a peptide with a chemically distinct butrecognized functional analog of the amino acid, i.e., an artificialamino acid analog. Artificial amino acid analogs include β-amino acids,β-substituted β-amino acids (“β³-amino acids”), phosphorous analogs ofamino acids, such as amino phosphonic acids and amino phosphinic acids,and amino acids having non-peptide linkages. Artificial amino acids canbe used to create peptidomimetics, such as peptoid oligomers (e.g.,peptoid amide or ester analogues), β-peptides, cyclic peptides,oligourea or oligocarbamate peptides; or heterocyclic ring molecules.

Also useful in the methods disclosed herein are nucleic acid moleculesthat encode SRPX agents described herein, e.g., naturally occurring SRPXpolypeptides or forms of SRPX polypeptides in which naturally occurringamino acid sequences are altered or deleted (e.g., fragments or analogsof SRPX). Certain nucleic acids can encode polypeptides that are solubleunder normal physiological conditions. SRPX agents can be expressed(e.g., exogenously expressed) within a cell by any means known in theart. To generate cells that express SRPX agents, the cells can betransfected, transformed, or transduced using any of a variety oftechniques known in the art. Any number of transfection, transformation,and transduction protocols known to those in the art may be used, forexample those outlined in Current Protocols in Molecular Biology, JohnWiley & Sons, New York, N.Y., or in numerous kits available commercially(e.g., Invitrogen Life Technologies, Carlsbad, Calif.). Such techniquesmay result in stable or transient transformants. One suitabletransfection technique is electroporation, which can be performed on avariety of cell types, including mammalian cells, yeast cells andbacteria, using commercially available equipment. Optimal conditions forelectroporation (including voltage, resistance and pulse length) areexperimentally determined for the particular host cell type, and generalguidelines for optimizing electroporation can be obtained frommanufacturers.

When the polypeptide expressed by a nucleic acid is intended to besecreted, the nucleic acid sequence can encode an N-terminal signalsequence that directs secretion of the polypeptide. In some embodiments,the signal sequence is a heterologous signal sequence. Signal sequencesthat function in prokaryotes and eukaryotes are well known, and one ofordinary skill can select or design an appropriate signal sequenceaccordingly. In some embodiments, the nucleic acid can encode a SRPXpolypeptide, variant, or fragment as disclosed herein with a SRPX orheterologous signal sequence.

Exemplary methods of administering SRPX agents include introducing intoa subject a nucleic acid that encodes an SRPX agent described herein. Insome embodiments, the nucleic acid that encodes the SRPX agent iscontained within a vector, e.g., as a virus that includes a nucleic acidthat expresses the SRPX agent. Exemplary viral vectors includeadenoviruses (reviewed in Altaras et al., 2005, Adv. Biochem. Eng.Biotechnol., 99:193-260), adeno-associated viruses (reviewed in Park etal., 2008, Front. Biosci., 13:2653-59; see also Williams, 2007, Mol.Ther., 15:2053-54), parvoviruses, lentiviruses, retroviruses (reviewedin Tai et al., 2008, Front. Biosci., 13:3083-95), and the herpes simplexvirus. Methods of delivery of nucleic acids are reviewed in Patil etal., 2005, AAPS J., 7:E61-77, which is incorporated herein by referencein its entirety.

An exemplary AAV vector containing a polypeptide that includes SEQ IDNO:1 is shown in FIG. 4B and has the sequence:

(SEQ ID NO: 3) attaggctgcgcgctcgctcgctcactgaggccgcccgggcaaagcccgggcgtcgggcgacctttggtcgcccggcctcagtgagcgagcgagcgcgcagagagggagtggccaactccatcactaggggttccttgtagttaatgattaacccgccatgctacttatctaccagggtaatggggatcctctagaactatagctagcatgcctgcaggctgaccgcccaacgacccccgcccattgacgtcaataatgacgtatgttcccatagtaacgccaatagggactttccattgacgtcaatgggtggagtatttacggtaaactgcccacttggcagtacatcaagtgtatcatatgccaagtccgccccctattgacgtcaatgacggtaaatggcccgcctggcattatgcccagtacatgaccttacgggactttcctacttggcagtacatctacgtattagtcatcgctattaccatggtgatgcggttttggcagtacaccaatgggcgtggatagcggtttgactcacggggatttccaagtctccaccccattgacgtcaatgggagtttgttttggcaccaaaatcaacgggactttccaaaatgtcgtaataaccccgccccgttgacgcaaatgggcggtaggcgtgtacggtgggaggtctatataagcagagctcgtttagtgaaccgtcagatcactagaagctttattgcggtagtttatcacagttaaattgctaacgcagtcagtgcttctgacacaacagtctcgaacttaagctgcagaagttggtcgtgaggcactgggcaggtaagtatcaaggttacaagacaggtttaaggagaccaatagaaactgggcttgtcgagacagagaagactcttgcgtttctgataggcacctattggtcttactgacatccactttgcctttctctccacaggtgtccactcccagttcaattacagctcttaaggctagagtacttaatacgactcactataggctagcctcgagaattcacgcgtggtacggtaccatgatggagacagacacactcctgctatgggtactgctgctctgggttccaggttccactggtgacgcggcccagccggccaggcgcgcgcgccgtacgaagcttgactcaccactagaagacgatgaagtcgggtattcacaccctagatataaagataccccgtggtgctcccccatcaaggtgaagtatggggatgtgtactgcagggcccctcaaggaggatactacaaaacagccctgggaaccaggtgcgacattcgctgccagaagggctacgagctgcatggctcttccctactgatctgccagtcaaacaaacgatggtctgacaaggtcatctgcaaacaaaagcgatgtcctacccttgccatgccagcaaatggagggtttaagtgtgtagatggtgcctactttaactcccggtgtgagtattattgttcaccaggatacacgttgaaaggggagcggaccgtcacatgtatggacaacaaggcctggagcggccggccagcctcctgtgtggatatggaacctcctagaatcaagtgcccaagtgtgaaggaacgcattgcagaacccaacaaactgacagtccgggtgtcctgggagacacccgaaggaagagacacagcagatggaattcttactgatgtcattctaaaaggcctccccccaggctccaactttccagaaggagaccacaagatccagtacacagtctatgacagagctgagaataagggcacttgcaaatttcgagttaaagtaagagtcaaacgctgtggcaaactcaatgccccagagaatggttacatgaagtgctccagcgacggtgataattatggagccacctgtgagttctcctgcatcggcggctatgagctccagggtagccctgcccgagtatgtcaatccaacctggcttggtctggcacggagcccacctgtgcagccatgaacgtcaatgtgggtgtcagaacggcagctgcacttctggatcagttttatgagaaaaggagactcctcattgtgtccacacccacagcccgaaacctcctttaccggctccagctaggaatgctgcagcaagcacagtgtggccttgatcttcgacacatcaccgtggtggagctggtgggtgtgttcccgactctcattggcaggataggagcaaagattatgcctccagccctagcgctgcagctcaggctgttgctgcgaatcccactctactccttcagtatggtgctagtggataagcatggcatggacaaagagcgctatgtctccctggtgatgcctgtggccctgttcaacctgattgacacttttcccttgagaaaagaagagatggtcctacaagccgaaatgagccagacctgtaacaccgctcgaggagggcccgaacaaaaactcatctcagaagagaatctgaatagcgccgtcgaccatcatcatcatcatcattgaggtaccctctagagtcgacccgggcggcctcgaggacggggtgaactacgcctgaggatccgatctttttccctctgccaaaaattatggggacatcatgaagccccttgagcatctgacttctggctaataaaggaaatttattttcattgcaatagtgtgttggaattttttgtgtctctcactcggaagcaattcgttgatctgaatttcgaccacccataatacccattaccctggtagataagtagcatggcgggttaatcattaactacaaggaacccctagtgatggagttggccactccctctctgcgcgctcgctcgctcactgaggccgggcgaccaaaggtcgcccgacgcccgggctttgcccgggcggcctcagtgagcgagcgagcgcgcagccttaattaatta attaaggcctta

An exemplary AAV vector containing a polypeptide that includes SEQ IDNO:2 is shown in FIG. 5B and has the sequence:

(SEQ ID NO: 4) attaggctgcgcgctcgctcgctcactgaggccgcccgggcaaagcccgggcgtcgggcgacctttggtcgcccggcctcagtgagcgagcgagcgcgcagagagggagtggccaactccatcactaggggttccttgtagttaatgattaacccgccatgctacttatctaccagggtaatggggatcctctagaactatagctagcatgcctgcaggctgaccgcccaacgacccccgcccattgacgtcaataatgacgtatgttcccatagtaacgccaatagggactttccattgacgtcaatgggtggagtatttacggtaaactgcccacttggcagtacatcaagtgtatcatatgccaagtccgccccctattgacgtcaatgacggtaaatggcccgcctggcattatgcccagtacatgaccttacgggactttcctacttggcagtacatctacgtattagtcatcgctattaccatggtgatgcggttttggcagtacaccaatgggcgtggatagcggtttgactcacggggatttccaagtctccaccccattgacgtcaatgggagtttgttttggcaccaaaatcaacgggactttccaaaatgtcgtaataaccccgccccgttgacgcaaatgggcggtaggcgtgtacggtgggaggtctatataagcagagctcgtttagtgaaccgtcagatcactagaagctttattgcggtagtttatcacagttaaattgctaacgcagtcagtgcttctgacacaacagtctcgaacttaagctgcagaagttggtcgtgaggcactgggcaggtaagtatcaaggttacaagacaggtttaaggagaccaatagaaactgggcttgtcgagacagagaagactcttgcgtttctgataggcacctattggtcttactgacatccactttgcctttctctccacaggtgtccactcccagttcaattacagctcttaaggctagagtacttaatacgactcactataggctagcctcgagaattcacgcgtggtacggtaccatggggagccccgcacatcggcccgcgctgctgctgctgctgccgcctctgctgctgctgctgctgctgcgcgtcccgcccagccgcagcttcccaggatcgggagactcaccactagaagacgatgaagtcgggtattcacaccctagatataaagataccccgtggtgctcccccatcaaggtgaagtatggggatgtgtactgcagggcccctcaaggaggatactacaaaacagccctgggaaccaggtgcgacattcgctgccagaagggctacgagctgcatggctcttccctactgatctgccagtcaaacaaacgatggtctgacaaggtcatctgcaaacaaaagcgatgtcctacccttgccatgccagcaaatggagggtttaagtgtgtagatggtgcctactttaactcccggtgtgagtattattgttcaccaggatacacgttgaaaggggagcggaccgtcacatgtatggacaacaaggcctggagcggccggccagcctcctgtgtggatatggaacctcctagaatcaagtgcccaagtgtgaaggaacgcattgcagaacccaacaaactgacagtccgggtgtcctgggagacacccgaaggaagagacacagcagatggaattcttactgatgtcattctaaaaggcctccccccaggctccaactttccagaaggagaccacaagatccagtacacagtctatgacagagctgagaataagggcacttgcaaatttcgagttaaagtaagagtcaaacgctgtggcaaactcaatgccccagagaatggttacatgaagtgctccagcgacggtgataattatggagccacctgtgagttctcctgcatcggcggctatgagctccagggtagccctgcccgagtatgtcaatccaacctggcttggtctggcacggagcccacctgtgcagccatgaacgtcaatgtgggtgtcagaacggcagctgcacttctggatcagttttatgagaaaaggagactcctcattgtgtccacacccacagcccgaaacctcctttaccggctccagctaggaatgctgcagcaagcacagtgtggccttgatcttcgacacatcaccgtggtggagctggtgggtgtgttcccgactctcattggcaggataggagcaaagattatgcctccagccctagcgctgcagctcaggctgttgctgcgaatcccactctactccttcagtatggtgctagtggataagcatggcatggacaaagagcgctatgtctccctggtgatgcctgtggccctgttcaacctgattgacacttttcccttgagaaaagaagagatggtcctacaagccgaaatgagccagacctgtaacaccgaacaaaaactcatctcagaagaggatctgaatagcgccgtcgaccatcatcatcatcatcattgaggtaccctctagagtcgacccgggcggcctcgaggacggggtgaactacgcctgaggatccgatctttttccctctgccaaaaattatggggacatcatgaagccccttgagcatctgacttctggctaataaaggaaatttattttcattgcaatagtgtgttggaattttttgtgtctctcactcggaagcaattcgttgatctgaatttcgaccacccataatacccattaccctggtagataagtagcatggcgggttaatcattaactacaaggaacccctagtgatggagttggccactccctctctgcgcgctcgctcgctcactgaggccgggcgaccaaaggtcgcccgacgcccgggctttgcccgggcggcctcagtgagcgagcgagcgcgcagccttaattaattaattaaggcctta

In some embodiments, a nucleic acid that expresses a SRPX polypeptide isadministered directly to cancer cells or to cells in the vicinity of thecancer cells. In some embodiments, a nucleic acid that expresses a SRPXpolypeptide is administered to a cell ex vivo, which is thenadministered to the subject in the vicinity of the tumor.

A SRPX agent can be produced by any means known in the art, e.g., bychemical synthesis, recombinant methods, or isolation from cells thatnaturally produce SRPX. Methods of purification and isolation ofmolecules that include polypeptides are also well known to those ofskill in the art.

Production of Fragments and Analogs of SRPX

Generation of Fragments

Fragments of a protein can be produced in several ways, e.g.,recombinantly, by proteolytic digestion, or by chemical synthesis.Internal or terminal fragments of a polypeptide can be generated byremoving one or more nucleotides from one end (for a terminal fragment)or both ends (for an internal fragment) of a nucleic acid that encodesthe polypeptide. Expression of the mutagenized DNA produces polypeptidefragments. Digestion with “end-nibbling” endonucleases can thus generateDNAs that encode an array of fragments. DNAs that encode fragments of aprotein can also be generated by random shearing, restriction digestionor a combination of the above-discussed methods.

Fragments can also be chemically synthesized using techniques known inthe art such as conventional Merrifield solid phase f-Moc or t-Bocchemistry. For example, peptides of the present invention can bearbitrarily divided into fragments of desired length with no overlap ofthe fragments, or divided into overlapping fragments of a desiredlength.

Generation of Analogs: Production of Altered DNA and Peptide Sequencesby Random Methods

Amino acid sequence variants of a protein can be prepared by randommutagenesis of DNA which encodes a protein or a particular domain orregion of a protein. Useful methods include PCR mutagenesis andsaturation mutagenesis. A library of random amino acid sequence variantscan also be generated by the synthesis of a set of degenerateoligonucleotide sequences. (Methods for screening proteins in a libraryof variants are elsewhere herein.)

PCR Mutagenesis

In PCR mutagenesis, reduced Taq polymerase fidelity is used to introducerandom mutations into a cloned fragment of DNA (Leung et al., 1989,Technique 1:11-15). This is a very powerful and relatively rapid methodof introducing random mutations. The DNA region to be mutagenized isamplified using the polymerase chain reaction (PCR) under conditionsthat reduce the fidelity of DNA synthesis by Taq DNA polymerase, e.g.,by using a dGTP/dATP ratio of five and adding Mn²⁺ to the PCR reaction.The pool of amplified DNA fragments is inserted into appropriate cloningvectors to provide random mutant libraries.

Saturation Mutagenesis

Saturation mutagenesis allows for the rapid introduction of a largenumber of single base substitutions into cloned DNA fragments (Mayers etal., 1985, Science 229:242). This technique includes generation ofmutations, e.g., by chemical treatment or irradiation of single-strandedDNA in vitro, and synthesis of a complimentary DNA strand. The mutationfrequency can be modulated by modulating the severity of the treatment,and essentially all possible base substitutions can be obtained. Becausethis procedure does not involve a genetic selection for mutant fragmentsboth neutral substitutions, as well as those that alter function, areobtained. The distribution of point mutations is not biased towardconserved sequence elements.

Degenerate Oligonucleotides

A library of homologs can also be generated from a set of degenerateoligonucleotide sequences. Chemical synthesis of a degenerate sequencescan be carried out in an automatic DNA synthesizer, and the syntheticgenes then ligated into an appropriate expression vector. The synthesisof degenerate oligonucleotides is known in the art (see for example,Narang, S A (1983) Tetrahedron 39:3; Itakura et al. (1981) RecombinantDNA, Proc 3rd Cleveland Sympos. Macromolecules, ed. A G Walton,Amsterdam: Elsevier pp 273-289; Itakura et al. (1984) Annu. Rev.Biochem. 53:323; Itakura et al. (1984) Science 198:1056; Ike et al.(1983) Nucleic Acid Res. 11:477. Such techniques have been employed inthe directed evolution of other proteins (see, for example, Scott et al.(1990) Science 249:386-390; Roberts et al. (1992) PNAS 89:2429-2433;Devlin et al. (1990) Science 249: 404-406; Cwirla et al. (1990) PNAS 87:6378-6382; as well as U.S. Pat. Nos. 5,223,409, 5,198,346, and5,096,815).

Generation of Analogs: Production of Altered DNA and Peptide Sequencesby Directed Mutagenesis

Non-random or directed, mutagenesis techniques can be used to providespecific sequences or mutations in specific regions. These techniquescan be used to create variants that include, e.g., deletions,insertions, or substitutions, of residues of the known amino acidsequence of a protein. The sites for mutation can be modifiedindividually or in series, e.g., by (1) substituting first withconserved amino acids and then with more radical choices depending uponresults achieved, (2) deleting the target residue, or (3) insertingresidues of the same or a different class adjacent to the located site,or combinations of options 1-3.

Alanine Scanning Mutagenesis

Alanine scanning mutagenesis is a useful method for identification ofcertain residues or regions of the desired protein that are preferredlocations or domains for mutagenesis, Cunningham and Wells (Science244:1081-1085, 1989). In alanine scanning, a residue or group of targetresidues are identified (e.g., charged residues such as Arg, Asp, His,Lys, and Glu) and replaced by a neutral or negatively charged amino acid(most preferably alanine or polyalanine). Replacement of an amino acidcan affect the interaction of the amino acids with the surroundingaqueous environment in or outside the cell. Those domains demonstratingfunctional sensitivity to the substitutions are then refined byintroducing further or other variants at or for the sites ofsubstitution. Thus, while the site for introducing an amino acidsequence variation is predetermined, the nature of the mutation per seneed not be predetermined. For example, to optimize the performance of amutation at a given site, alanine scanning or random mutagenesis can beconducted at the target codon or region and the expressed desiredprotein subunit variants are screened for the optimal combination ofdesired activity.

Oligonucleotide-Mediated Mutagenesis

Oligonucleotide-mediated mutagenesis is a useful method for preparingsubstitution, deletion, and insertion variants of DNA, see, e.g.,Adelman et al., (DNA 2:183, 1983). Briefly, the desired DNA is alteredby hybridizing an oligonucleotide encoding a mutation to a DNA template,where the template is the single-stranded form of a plasmid orbacteriophage containing the unaltered or native DNA sequence of thedesired protein. After hybridization, a DNA polymerase is used tosynthesize an entire second complementary strand of the template thatwill thus incorporate the oligonucleotide primer, and will code for theselected alteration in the desired protein DNA. Generally,oligonucleotides of at least 25 nucleotides in length are used. Anoptimal oligonucleotide will have 12 to 15 nucleotides that arecompletely complementary to the template on either side of thenucleotide(s) coding for the mutation. This ensures that theoligonucleotide will hybridize properly to the single-stranded DNAtemplate molecule. The oligonucleotides are readily synthesized usingtechniques known in the art such as that described by Crea et al. (Proc.Natl. Acad. Sci. (1978) USA, 75: 5765).

Cassette Mutagenesis

Another method for preparing variants, cassette mutagenesis, is based onthe technique described by Wells et al. (Gene (1985) 34:315). Thestarting material is a plasmid (or other vector) that includes theprotein subunit DNA to be mutated. The codon(s) in the protein subunitDNA to be mutated are identified. There must be a unique restrictionendonuclease site on each side of the identified mutation site(s). If nosuch restriction sites exist, they can be generated using theabove-described oligonucleotide-mediated mutagenesis method to introducethem at appropriate locations in the desired protein subunit DNA. Afterthe restriction sites have been introduced into the plasmid, the plasmidis cut at these sites to linearize it. A double-stranded oligonucleotideencoding the sequence of the DNA between the restriction sites butcontaining the desired mutation(s) is synthesized using standardprocedures. The two strands are synthesized separately and thenhybridized together using standard techniques. This double-strandedoligonucleotide is referred to as the cassette. This cassette isdesigned to have 3′ and 5′ ends that are comparable with the ends of thelinearized plasmid, such that it can be directly ligated to the plasmid.This plasmid now contains the mutated desired protein subunit DNAsequence.

Combinatorial Mutagenesis

Combinatorial mutagenesis can also be used to generate mutants. Forexample, the amino acid sequences for a group of homologs or otherrelated proteins are aligned, preferably to promote the highest homologypossible. All of the amino acids that appear at a given position of thealigned sequences can be selected to create a degenerate set ofcombinatorial sequences. The variegated library of variants is generatedby combinatorial mutagenesis at the nucleic acid level, and is encodedby a variegated gene library. For example, a mixture of syntheticoligonucleotides can be enzymatically ligated into gene sequences suchthat the degenerate set of potential sequences are expressible asindividual peptides, or alternatively, as a set of larger fusionproteins containing the set of degenerate sequences.

Primary High-Through-Put Methods for Screening Libraries of PeptideFragments or Homologs

Various techniques are known in the art for screening generated mutantgene products. Techniques for screening large gene libraries ofteninclude cloning the gene library into replicable expression vectors,transforming appropriate cells with the resulting library of vectors,and expressing the genes under conditions in which detection of adesired activity, e.g., inhibition of growth of human cancer cell lines(e.g., NCI-H23, EKVX, HOP-62, HOP-92, HCT-15, SW-620, COLO205, HT29,HCT-116, KM-12, CCRF-CEM, K-562, MOLT-4, SR, RPMI-8226, A549-ATCC,NCI-H226, NCI-H322M) is measured. Each of the techniques described belowis amenable to high through-put analysis for screening large numbers ofsequences created, e.g., by random mutagenesis techniques.

Cancers

The new methods can be used to treat several types of cancer, e.g., lungcancers (e.g., adenocarcinoma, nonsmall cell lung cancer), colorectalcancers, thyroid cancers (e.g., papillary thyroid carcinoma, anaplasticthyroid carcinoma, follicular carcinoma, follicular adenoma), lymphomas(e.g., non-Hodgkin lymphoma), multiple myeloma, leukemias, breastcancers, ovarian cancers, gastric cancers, bladder cancers, pancreaticcancers, gall bladder cancers, bile duct cancers, and other carcinomas.In some embodiments, the present methods can be used to treat a subjecthaving an epithelial cancer, e.g., a solid tumor of epithelial origin,e.g., lung, breast, ovarian, prostate, renal, pancreatic, or coloncancer. Methods of diagnosing cancers are well known to those of skillin the art.

In addition, the methods described herein can include identifying thecancer as lacking SRPX expression. A number of methods for detectinglevels of SRPX expression are known in the art. In some embodiments,levels of SRPX mRNA are detected in cells from the tumor; alternativelyor in addition, levels or SRPX polypeptide are detected in a samplecomprising tissue or cells from the tumor. See, e.g., Yamashita et al.1999, Oncogene 18:4777; Tambe et al. 2009, Cancer Lett 283:74; Kim et a.2003, Hum Pathol 34:654; Mukaisho et al. 2002, Jpn J Cancer Res 93:888;Shimakage et al. 2000, Int J Cancer 87:5; Shimakage et al. 2002, HumPathol 33:615; Shimakage et al. 2009, Oncol Rep 21:1367; and Tambe etal. 2007, Carcinogenesis 28(4):777-784, all of which are incorporatedherein by reference.

Pharmaceutical Formulations

The SRPX agents described herein (all of which can be referred to hereinas “active compounds”), can be incorporated into pharmaceuticalcompositions. Such compositions typically include the active compoundand a pharmaceutically acceptable carrier or excipient. A“pharmaceutically acceptable carrier” can include solvents, dispersionmedia, coatings, antibacterial and antifungal agents, isotonic andabsorption delaying agents, and the like, compatible with pharmaceuticaladministration. Supplementary active compounds can also be incorporatedinto the compositions.

There are a number of methods by which the new compositions for use inthe new methods can be delivered to subjects, in general, and tospecific cells or tissue in those subjects, in particular. For example,a SRPX agent (e.g., a polypeptide or active fragment thereof) asdescribed herein can be injected into a subject or a tissue of thesubject. In another example, a vector (e.g., a plasmid or virus)encoding a SRPX agent can be introduced into a cell or tissue of thesubject. The vector would then enter the cell or cells in that tissueand express the SRPX agent. Delivery specificity of such plasmids can beenhanced by associating them with organ- or tissue-specific affinity, sothat they preferentially enter specified cell types; in preferredembodiments, the vector would enter cells in or near the tumor. BecauseSRPX can act extracellularly, it is not necessary to deliver the vectordirectly to tumor cells. The vector can be delivered to the tissuesurrounding the tumor, or cells expressing and secreting SRPX can bedelivered to a site near the tumor. Similarly, when SRPX polypeptides oractive fragments thereof are administered, the active agents need notenter the cells, but are delivered to the extracellular surface. Methodsof expressing proteins for tumor therapy are described, e.g., in Crossand Burmester, 2006, Clin. Med. Res., 4:218-227; Lejuene et al., 2007,Expert Rev. Anticancer Ther. 7:701-713; and Bloquel et al., 2004, J.Gene Med., 6:S11-S23.

Compounds and their physiologically acceptable salts and solvates can beformulated for oral, topical, buccal, parenteral or rectaladministration or administration by inhalation or insufflation (eitherthrough the mouth or the nose).

The compounds will generally be formulated for parenteral administrationby injection, for example, by bolus injection or continuous infusion.Formulations for injection can be presented in unit dosage form, forexample, in ampoules or in multi-dose containers, with an addedpreservative. The compositions can take such forms as suspensions,solutions or emulsions in oily or aqueous vehicles, and can containformulatory agents such as suspending, stabilizing and/or dispersingagents. Alternatively, the active ingredient can be in powder form forconstitution with a suitable vehicle, for example, sterile pyrogen-freewater, before use. Where the compositions are intended for use in aspecific treatment area, the compositions can be administered by one ormore local injections into the tumor site to diminish as much aspossible any side effects relating to the compound's activities outsideof the treatment area.

In addition to the formulations described previously, the compounds canalso be formulated as a depot preparation. Such long acting formulationscan be administered by implantation (for example subcutaneously orintramuscularly) or by intramuscular injection. Thus, for example, thecompounds can be formulated with suitable polymeric or hydrophobicmaterials (for example as an emulsion in an acceptable oil) or ionexchange resins, or as sparingly soluble derivatives, for example, as asparingly soluble salt. A depot preparation can include embedded orencapsulated cells or tissue that secrete a SRPX agent, which can beadministered, e.g., by implantation or by intramuscular injection.

The compositions can, if desired, be presented in a pack or dispenserdevice that can contain one or more unit dosage forms containing theactive ingredient. The pack can, for example, include metal or plasticfoil, such as a blister pack. The pack or dispenser device can beaccompanied by instructions for administration.

The therapeutic compositions of the invention can also contain a carrieror excipient, many of which are known to skilled artisans. Methods formaking such formulations are well known and can be found in, forexample, Remington: The Science and Practice of Pharmacy, University ofthe Sciences in Philadelphia (USIP), 2005.

The SRPX-encoding nucleic acid compositions can also be formulated forintracellular delivery of the active compounds, using methods known inthe art. For example, the compositions can include liposomes or othercarriers that deliver the active compound across the plasma membrane.Vesicles that are covered with membrane-permeant peptides, such as Tator Antennapedia, can also be used. A number of other methods forenhancing intracellular delivery are familiar to those of skill in theart. Such methods are not needed when the SRPX polypeptides or fragmentsthereof are used, as the SRPX polypeptides act extracellularly, and arethus delivered to the extracellular surface of the tumor cells. Thus insome embodiments, the methods include the use of a compositioncomprising a SRPX polypeptide or active fragment thereof, but notincluding any cell membrane permeation-enhancing compounds, e.g., thecomposition does not include liposomes or membrane-permeant peptides.

It is recognized that the pharmaceutical compositions and methodsdescribed herein can be used independently or in combination with oneanother. That is, subjects can be administered one or more of thepharmaceutical compositions, e.g., pharmaceutical compositions thatinclude a SRPX agent, subjected to one or more of the therapeuticmethods described herein, or both, in temporally overlapping ornon-overlapping regimens. When therapies overlap temporally, thetherapies can generally occur in any order and can be simultaneous(e.g., administered simultaneously together in a composite compositionor simultaneously but as separate compositions) or interspersed. By wayof example, a subject afflicted with a disorder described herein can besimultaneously or sequentially administered both a cytotoxic agent whichselectively kills aberrant cells and an antibody (e.g., an antibody ofthe invention) which can, in one embodiment, be conjugated or linkedwith a therapeutic agent, a cytotoxic agent, an imaging agent, or thelike.

Effective Doses

Toxicity and therapeutic efficacy of a SRPX agent can be determined bystandard pharmaceutical procedures, using either cells in culture orexperimental animals to determine the LD50 (the dose lethal to 50% ofthe population) and the ED50 (the dose therapeutically effective in 50%of the population). The dose ratio between toxic and therapeutic effectsis the therapeutic index and it can be expressed as the ratio LD50/ED50.Inhibitors that exhibit large therapeutic indices are preferred. Whileinhibitors that exhibit toxic side effects can be used, care can betaken to design a delivery system that targets such compounds to thesite of affected tissue to minimize potential damage to non-target cellsand, thereby, reduce side effects.

The data obtained from the cell culture assays and animal studies can beused in formulating a range of dosage for use in humans. The dosage ofsuch compounds lies preferably within a range of circulatingconcentrations that include the ED50 with little or no toxicity. Thedosage can vary within this range depending upon the dosage formemployed and the route of administration utilized. For any compound usedin the new methods, the therapeutically effective dose can be estimatedinitially from cell culture assays. A dose can also be calculated inanimal models to achieve a circulating plasma concentration range thatincludes the IC50 (that is, the concentration of the test compound whichachieves a half-maximal inhibition of symptoms) as determined in cellculture. Such information can be used to more accurately determineuseful doses in humans.

EXAMPLES Example 1 SRPX Inhibits the Growth of Cancer Cells and LungCancer Xenografts

Quantitative reverse transcription-polymerase chain reaction (qRT-PCR)analysis was performed to monitor SRPX expression in 9 normal lungsamples, 14 lung adenocarcinoma samples, and 6 lung squamous cellcarcinoma samples. Total RNA from the human samples was obtained fromthe University of Massachusetts Medical School Cancer Center TissueBank. Reverse transcription was performed using SuperScript™ II ReverseTranscriptase (Invitrogen) and an oligo(dT) primer (Invitrogen),followed by quantitative PCR using Fast SYBR™ Green Master Mix (AppliedBiosystems) and gene-specific primers for SRPX. For each sample,expression of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) providedan internal normalization control. For normal lung samples, the averageof the 9 samples is shown. Error bars indicate standard deviation. SRPXexpression was significantly decreased relative to normal lung tissue inall squamous cell carcinoma samples and at least 13 of 14 lungadenocarcinoma samples (FIG. 1A).

To determine if SRPX could affect growth of cancer cells, several lungcancer cell lines and, as a control, the normal lung cell line MRC5,were plated in 6-well plates (3×10⁵ cells per well), treated with orwithout 10 μg/ml recombinant SRPX (rSRPX) and stained with crystalviolet. To express and purify rSRPX, an SRPXsec expression constructincluding a nucleic acid encoding SEQ ID NO:1 with a heterologous signalsequence and Myc and His₆ tags was transfected into FreeStyle™ ChineseHamster Ovary (CHO) cells (Invitrogen), and conditioned medium wascollected 96 hours later and incubated with TALON™ Metal Affinity Resin(Clontech) to purify the His₆-tagged SRPX protein. The purified proteinwas dialyzed in phosphate buffered saline (PBS) to remove free salts.rSRPX decreased growth of the cancer cell lines tested but had no effecton the growth of the normal lung cell line (FIG. 1B).

To investigate the effect of SRPX on tumors in vivo, 5×10⁶ A549 humanalveolar adenocarcinoma cells (mixed with Matrigel™ matrix in a volumeof 100 μl) were injected subcutaneously into the right flank of femaleBALB/c nu/nu (nude) mice (n=2 mice per experimental group). Three dayslater, the mice were injected into the anterior tibialis muscle of theleft leg with either 3.0×10¹¹ particles of AAV-SRPXwt or, as a control,AAV-LacZ. Tumor dimensions were measured on days 7, 11, 17, 23, 30 and38 after injection, and tumor volume was calculated using the formulaπ/6×(length)×(width)². Error bars indicate standard deviation. AAV-SRPXsignificantly reduced tumor growth at days 30 and 38 as compared to thecontrol (FIG. 1C).

In another experiment, about 10⁶ A549 cells were injected in Balb/cNu/Nu mice, and AAv9-SRPX virus was injected when the tumors reached thesize of 250 mm³. The results, shown in FIG. 1D, are for two mice pergroup as one animal in the control group failed to develop the tumor andone animal in SRPX group developed an abnormal mass around the belly.The difference in tumor growth is very significant.

To determine whether in vivo administration of SRPX was associated withsignificant toxicity, increasing doses were administered to mice andlevels of liver enzymes, aspartate aminotransferase (AST) and alanineaminotransferase (ALT), increases in which are typically associated withtoxic insult, were measured. The results, as shown in FIGS. 1E (ALT) and1F (AST), demonstrated that SRPX has no detectable liver toxicity at thedoses tested.

The NCI60 panel of human cancer cell lines (see Shoemaker, 2006, Nat.Rev. Cancer, 6:813-823) was obtained from the National Cancer Institute.The panel includes cell lines corresponding to breast (MDA-MB-231, HS578T, 8T-549, T47-D, MCF7), ovarian (NCI-ADR-RES, OVCAR-3, OVCAR-5,OVCAR-8, OVCAR-4, SK-OV-3, IGROV1), prostate (DU-145, PC-3), renal(TK-10, CAKI-1, A496, ACHN, RXF-393, 786-0, SN12C, UO-31),non-small-cell lung (NCI-H460, HOP-62, A549-ATCC, NCI-H226, EKVX,NCI-H322M, HOP-92, NCI-H522), central nervous system (CNS) (SF-295,SF-268, SF-539, SNB-19, SNB-75, U251), colon (HCT-15, SW-620, COLO205,HT29, HCC-2998, HCT-116, KM-12), melanoma (SK-MEL-28, SK-M2L-2, LOXIMVI, M14, MALM-3M, SK-MEL-5, UACC-257, UACC-62, MDA-MB-435), andhematopoietic (CCRF-CEM, K-562, MOLT-4, SR, RPMI-8226) cancers (only asubset of the NCI60 panel is shown). Cells (3×10⁵ for breast, colon,leukemia, lung cell lines, and 2×105 for melanoma cell lines) wereplated and treated with 30% control CM or SRPX-containing CM (producedas described above for FIG. 1B), or left untreated. After 3 days, the CMwas replaced with complete medium, and the cells allowed were to growfor an additional 4 days before staining with crystal violet. Percentgrowth was calculated relative to the untreated control cells, which wasset to 100%. Error bars indicate standard deviation. The results showthat in addition to lung cancer, SRPX inhibits the growth of severalother cancer cell types, including breast cancer, colon cancer, andleukemia cell lines (FIG. 2).

As a secreted protein, SRPX contains an N-terminal signal sequence thatdirects its secretion. To determine whether the signal sequence isrequired for the ability of SRPX to inhibit cancer cell growth, aderivative of full-length SRPX that lacks the N-terminal signal sequence(amino acids 1-35; hereafter called SRPX(Δ1-35)) was constructed andtested for its ability to inhibit growth of A549 human lungadenocarcinoma epithelial cells. Briefly, 3×10⁵ A549 cells were platedin 6-well plates and treated with 30% CM derived from cells expressingeither empty vector (control), full-length SRPX or SRPX(Δ1-35). After 3days, the CM was replaced with complete medium, and the cells wereallowed to grow for an additional 4 days before staining with crystalviolet. The results show that in contrast to full-length SRPX,SRPX(Δ1-35) does not inhibit growth of A549 cells (FIG. 3A). To confirmthese results, the ability of SRPX(Δ1-35) was analyzed for its abilityto kill A549 cells using an apoptosis assay. A549 cells (1.5×10⁶) weretransfected with a construct expressing either full-length SRPX orSRPX(Δ1-35), and 48 hours later were stained with Annexin V and 7 AAD(BD Bioscience) and analyzed by fluorescence-activated cell sorting(FACS). The results show that SRPX(Δ1-35) did not induce apoptosiscompared to full-length SRPX. Immunoblot analysis confirmed thatSRPX(Δ1-35) is expressed at roughly equivalent levels to full-lengthSRPX but, as expected, is not secreted into the CM (FIG. 3C).Collectively, the results show that secretion of SRPX is required forcell killing and that SRPX mediates cell killing extracellularly.

These results strongly support the use of SRPX to treat and prevent awide range of cancers, including lung cancers, colon cancers, andleukemias.

Other Embodiments

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

What is claimed is:
 1. A method of treating a solid tumor in a mammaliansubject, the method comprising: identifying a subject having a solidtumor; administering to the subject an effective amount of a therapeuticcomposition comprising an SRPX polypeptide that is at least 80%identical to SEQ ID NO:1, wherein the composition is administered to theextracellular surfaces of cells in the tumor by one or more localinjections into the tumor site, thereby treating the tumor.
 2. Themethod of claim 1, wherein the tumor is a carcinoma.
 3. The method ofclaim 1, wherein the tumor is a lung adenocarcinoma.
 4. The method ofclaim 1, wherein the tumor is a breast cancer, bladder cancer, ovariancancer, pancreatic cancer, colon cancer, colorectal cancer, or papillarythyroid carcinoma.
 5. The method of claim 1, wherein the SRPX agentcomprises a polypeptide at least 90% identical to SEQ ID NO:1.
 6. Themethod of claim 1, wherein the polypeptide is at least 95% identical toSEQ ID NO:1.